1. Field of the Invention
The present invention generally relates to a flat panel display such as, for example, a plasma display panel and, more particularly, to the flat panel display of a structure including a pair of substrates larger than a screen, in which one of the substrates has a peripheral edge partly protruding outwardly from that of the other of the substrates.
2. Description of the Prior Art
With keen interests centered on the environmental protection, various attempts have hitherto been made and are currently made in the field of industrial production of various products to minimize emission of industrial wastes. This is not an exception to the mass production of flat panel displays (FPDs) such as, for example, plasma display panels, liquid crystal panels, field emission display panels, organic electroluminescence panels and others. As is well understood by those skilled in the art, maximized utilization of materials contributes, to a large extent, to reduction in manufacturing cost and also to the environmental protection.
The plasma display panel is known, which emits imagewise light as a result of gas discharges developed in between a pair of substrates that are sandwiched together. In the plasma display panel of a type having a screen capable of achieving a matrix display, activation of a multiplicity of cells forming the display screen is controlled by column electrodes disposed on one of the substrates and row electrodes disposed on the other of the substrates. The column and row electrodes have respective ends drawn outwardly from the screen for electric connection with a matrix drive circuit as is well known to those skilled in the art.
By way of example, Japanese unexamined patent publication No. 8-255568, for example, discloses the use of flexible wiring boards for electrically connecting between the column and row electrodes and the matrix drive circuit, respectively. According to this published application, in order for the flexible wiring boards to be electrically connected with the column and row electrodes, respectively, by means of a heat press technique, the first and second substrates are sandwiched together so that respective ends of the column electrodes in the first substrate may protrude outwardly from the periphery of the second substrate while respective ends of the row electrodes in the second substrate may similarly protrude outwardly from the periphery of the first substrate.
Specifically, referring to FIG. 1, there is shown, in a schematic top plan view, the structure of the conventional plasma display panel. This conventional plasma display panel 1z shown therein includes first and second substrates 11z and 21z of a generally or substantially rectangular configuration each having a size larger than the display screen 51z. More particularly, while each of the first and second substrates 11z and 21z has a pair of short side edges opposite to each other and a pair of long side edges opposite to each other, the short side edges of one of the first and second substrates, for example, the second substrate 21z have a length c longer by about 1 cm than the length a of those of the first substrate 11z whereas the long side edges of the first substrate 11z have a length b longer by about 1 cm than the length d of those of the second substrate 21z. 
The first and second substrates 11z and 21z of different sizes as discussed above are positioned one above the other with their geometric centers aligned with each other. In this condition, the short side edges of the first substrate 11z protrude longitudinally outwardly, each a distance of about 5 mm, from those of the second substrate 21z in a horizontal direction, whereas the long side edges of the second substrate 21z protrude longitudinally outwardly, each a distance of about 5 mm, from those of the first substrate 11z in a direction orthogonal to the horizontal direction, that is, in a vertical direction.
It has, however, been found that as shown in and discussed with reference to FIGS. 2A and 2B, manufacture of the plasma display panel of a type utilizing the substrates of different sizes such as used in the conventional plasma display panel discussed above tends to yield a substantial amount of wastes resulting from sectioning, trimming, or otherwise cutting of the material for each of the first and second substrates.
More specifically, FIG. 2A illustrates two mother substrates 1001 and 1002 of the same size, which, when trimmed as will be discussed subsequently, eventually form the first and second substrates 11z and 21z of the different sizes. Considering that the first and second mother substrates 1001 and 1002 are of the same size, i.e., of a size that does not result in any lateral protrusion of any part of the mother substrates 1001 and 1002, trimming of the first mother substrate 1001 along one short side edge portion thereof to provide the first substrate 11z results in an elongated scrap 91 and, similarly, trimming of the second mother substrate 1002 along one long side edge portion thereof to provide the second substrate 21z results in an elongated scrap 92. The resultant scraps 91 and 92 are, of course, a waste that is to be disposed of without being reused nor recycled and are no longer utilized in part or in entirety as a part of the plasma display panel.
Similarly, similar scraps 93 and 94 may result in even where a plurality of, for example, two, first substrates 11z1 and 11z2 and correspondingly two second substrates 21z1 and 21z2 are to be prepared from the mother substrates 2001 and 2002, respectively, as shown in FIG. 2B.
To minimize waste of the material for the substrates, the use may be contemplated of relatively large mother substrates each having a size that is an integer multiplication of the size of the respective substrate 11z1 or 21z1. However, the use of such large mother substrates requires complicated and costly maintenance and storage of two kinds of mother substrates of different sizes. As such, diversification of the materials of different sizes is undesirable because the cost of manufacture of the plasma display panels would eventually result in.
In view of the foregoing, the present invention has for its object to maximize the efficiency of utilization of mother substrates that are material for the substrates used in the flat display panel to form a screen.